It appears the environmental effects of a rocket explosion were mostly contained to the southern third of Wallops Island, a NASA environmental team said after a preliminary assessment of the island and surrounding areas.

An Orbital Sciences Antares rocket loaded with a Cygnus spacecraft full of cargo for the International Space Station burst into a fireball Tuesday, seconds after liftoff from a launch pad on the southern part of the island.

NASA Wallops Flight Facility's industrial hygienist collected air samples in the vicinity immediately after the explosion and found no hazardous substances in the air, according to a news release from NASA.

The areas sampled were the Wallops mainland, the Chincoteague causeway and Chincoteague Island.

Eyewitnesses on Chincoteague and at the NASA Wallops Visitor Center reported an acrid smell in the air a while after the explosion, and Atlantic resident Robert E. Johnson said he smelled fumes there soon after it happened.

An Orbital official shortly after the incident said solid fuel from the rocket's second stage and hypergolic fuel — hydrazine and nitrogen tetroxide — that powers the Cygnus spacecraft are of more concern environmentally than is the first-stage liquid fuel, composed of oxygen and kerosene.

"We have to handle that very carefully. We don't know yet what the condition of the second stage motor might be, so that's part of the investigation," Orbital Executive Vice President Frank Culbertson said at a briefing some three hours after the blast.

Culbertson and NASA officials warned people not to touch any debris they find, noting the chemicals in the spacecraft's fuel have to be handled properly.

"That's one reason we highly encourage people not to try to enter this area or get close to it, either from the water or the land, and certainly don't go souvenir hunting along the beach," he said.

If anyone finds debris, "definitely do not touch it and keep people away from it," he said.

More air, soil and water samples are being collected from near where the rocket exploded and will be compared to samples from control sites.

No oil sheens or other obvious signs of pollution to area waterways have been observed, according to the Coast Guard and the Virginia Marine Resources Commission.

NASA said no "obvious impacts to fish or wildlife resources" were found after initial assessments, but the environmental team will continue to monitor those.

Virginia Department of Environmental Quality spokesman Bill Hayden said while NASA is doing the actual monitoring of the rocket's environmental impact, the department has consulted with NASA to determine what should be looked for.

"We have been talking to NASA about monitoring air, water, soil — this will be done on-site as well as the surrounding area," he said.